1. Field
Embodiments of the present invention relate to a device used in spinal surgery.
2. Related Art
Stabilizers used for interspinous spinal stabilization using a surgical posterior approach are usually known in the form of one or several cooperating carrying elements situated in the interspinous space, ended with profiled sockets for spinous processes. Such stabilizers situated in the axis of the spine serve mainly for one-level stabilization of the adjoining vertebrae.
Solutions are also known in the form of lamellar or rod bearing elements with an adjustable length, installed in the interspinous space and comprising hook elements resting against on spinous processes. Such stabilizers can be used for supporting the spine on one and several levels.
The solutions described above are additionally provided with elements attached to the bone using screws, pins, other mechanical latches or flexible ligaments. In most of such solutions, elements are supported in spinous processes and this requires using a bilateral surgical approach.
An interspinous implant situated non-axially in relation to the spine is known from the patent application WO2007/127550, comprising superior and inferior bearing elements cooperating in a sliding way along the axis corresponding to the axis of the spine. Laterally separated bearing elements are ended with brackets for fastening onto superior and inferior spinal interspinous processes, respectively. In a folded position, the device is of the height allowing its installation between spinal processes and the interspinous space is increased by distraction of both elements.
An axial interspinous implant in the form of a frame embracing exteriorly vertebral processes is disclosed in the patent application WO2007/127694. The frame is in the form of a ring or its parts provided with holes situated on both sides of the axis, through which elastic bands are drawn out. The bands constitute bearing elements pulling off superior and inferior processes respectively to the superior and inferior part of the frame. The place of connection of the implant with the bone can be secured by sharp projections constituting an integral part of internal surfaces of the frame.
From the patent application US 2006/0241614 an interspinous implant is known which contains a bearing supporting part with profiled sockets located axially between adjoining spinous process and two hook elements connected by an elastic band which passes through the support. The hooks fasten the processes from the superior side preventing excessive flexion of the spinal motion segment. The patent application WO 01/91658 discloses a device and the method of its application for distraction of adjacent spinous processes. The device has got a bracket with a guide fastened by a connector to a laterally separated rod element ended with hooks, which embrace spinous processes. The construction of the device allows rotational movement between the bracket and the hook.
A multi-segment stabilizer for controlling the intervertebral space is known from the U.S. Pat. No. 4,611,582. It comprises a longitudinal, laterally separated bearing body and two laminar clamps. The clamps are in the form of two alternating hooks, both adapted for a rigid, bilateral embrace of a part of one vertebra. The body is dual, consisting of movable cooperating parts connected with each other by threaded elements fastening and adjusting body's length.
The U.S. Pat. No. 5,439,463 refers to a spinal device which consists of two clamp elements ended with hook parts: a fixed one with a rod setting the distance and an adjustable one. The surface of the rod and the corresponding surface of the adjustable clamp cooperate in a sliding way through toothed surfaces, and their cooperation is secured by a distance fastening element provided with a clamping ring and threaded screw.
A device for implantation and distraction of spinal spinous processes is known from the patent application WO 2008/085445. It consists of a longitudinal body and two sliding elements. Each of them is composed of the main part cooperating with the body and hook arms for support on the bone. In an embodiment of the device, the arms are provided with a rough surface increasing friction in the area of contact of the implant and a spinous process.
All the solutions described above do not secure steady, even, and controlled intraoperative distraction, which is the essential purpose of the treatment of spinal dysfunctions. Corrective actions are performed after previously locating the implant in the interspinous space, thus necessitating acquisitions of a dimensional series of types of implants and precise selection of the implant's dimension for the interspinous space. Most of the solutions are intended for being fastened to biomechanically weak interspinous processes and they are designed only for such a fastening. The use of such solutions is also limited to only one segment of the spine, especially in the lumbar segment or on the lumbosacral border. Constructions used in the above described solutions are frequently complicated and made up of many elements. Thus a surgeon is forced to use a wide surgical approach and to adjust surgically the spinous processes to the bearing surface of the implant. Yet another inconvenience of the solutions referred to above is their great surgical invasiveness resulting from the necessity of dissection of soft tissues from both sides of the spine and also from the necessity of disrupting the supraspinous ligament or its separation from processes and withdrawing during installation of the implant.